Good nutrition forms the foundation of a healthy pregnancy, but even the best diet often can't supply everything your growing baby needs. These 7 supplements are consistently recommended by obstetricians worldwide — here is what each one does, how much to take, and when to start.
Important: Always discuss supplements with your doctor or midwife before starting. Dosages may need adjusting based on your blood test results.
Quick Reference Table
| Supplement | Daily Dose | When to Start |
|---|---|---|
| Folic Acid | 400 mcg | Before conception through all trimesters |
| Iodine | 220 mcg | All trimesters |
| Vitamin D | 600 IU | All trimesters |
| Iron | 30 mg | Trimester 2 & 3 |
| Omega-3 DHA | 200 mg DHA | Trimester 2 & 3 |
| Calcium | 1,000 mg | Trimester 2 & 3 (twice daily) |
| Magnesium | 350 mg | Trimester 2 & 3 |
1. Folic Acid (Vitamin B9)
The most critical supplement of all
Folic acid (vitamin B9) is essential for neural tube development and helps prevent serious birth defects of the brain and spine — including spina bifida and anencephaly. The neural tube closes in weeks 3–5, before most women even know they are pregnant. That's why experts recommend starting folic acid before conception and continuing through at least week 12 — the whole of the first trimester.
Food sources of folate: leafy greens (spinach, kale), lentils, fortified cereals, asparagus, eggs, broccoli. However, food folate has lower bioavailability than supplemental folic acid — don't rely on diet alone.
2. Iron
Oxygen for you and your baby
Iron supports haemoglobin production, which carries oxygen to your baby. During pregnancy your blood volume increases by 40–50%, significantly raising iron demand. Iron deficiency anaemia is the most common pregnancy complication — it can cause premature birth, low birth weight and impaired cognitive development. Ask your doctor to test ferritin (iron stores), not just haemoglobin — our guide to blood tests in pregnancy gives the thresholds both are read against and explains why stores fall before the haemoglobin does.
Absorption tip: Take iron with vitamin C (e.g., a glass of orange juice) to improve absorption. Avoid taking it with calcium, as they compete for the same transporter.
Iron is also the most common cause of constipation in pregnancy — that guide covers alternate-day dosing and gentler formulations, both of which usually fix it without stopping the supplement.
3. Iodine
Brain development and thyroid function
Iodine is crucial for thyroid hormone production, which regulates your baby's brain and nervous system development. Your baby relies entirely on your thyroid hormones until week 10–12, when its own thyroid starts working. Severe iodine deficiency during pregnancy can cause cretinism and intellectual disability. Many women — especially those avoiding seafood and iodised salt — are deficient without knowing it.
4. Vitamin D
Bones, immunity and gestational diabetes prevention
Vitamin D is essential for calcium absorption, bone development, and immune function. Studies link adequate vitamin D levels to reduced risk of gestational diabetes and preeclampsia. Up to 40–60% of pregnant women are deficient — particularly in northern latitudes, during winter, or if you cover your skin. Your doctor can check your 25-OH vitamin D level and recommend a higher dose if needed.
5. Omega-3 (DHA/EPA)
Brain and eye development
Omega-3 fatty acids — particularly DHA — are vital for foetal brain and eye development. DHA accumulates rapidly in the foetal brain during the third trimester. Studies show omega-3 supplementation may reduce risk of preterm birth and postpartum depression. Choose algae-based DHA if you prefer plant-based options; fish oil is also effective.
Safe fish sources of DHA: cooked salmon, sardines, anchovies, trout, and tilapia — all low in mercury. Avoid shark, swordfish, king mackerel, and raw sushi — see the safe foods guide for the full mercury list.
6. Calcium
Bones, teeth, heart, muscles and nerves
Calcium is critical for your baby's developing skeleton, teeth, heart muscle, and nerve function. By week 29 your baby draws ~250 mg of calcium from your body every single day. If your dietary intake is low, your body extracts calcium from your own bones — increasing your risk of osteoporosis later in life. Take calcium in two split doses for better absorption; it also competes with iron so take them at different times.
7. Magnesium
Leg cramps, sleep, blood pressure and stress
Magnesium helps regulate blood sugar and blood pressure, supports muscle and nerve function, and significantly reduces leg cramps — one of the most common complaints in mid-to-late pregnancy, alongside back pain and swelling. It also plays a role in bone development and protein synthesis. Magnesium glycinate and magnesium citrate are the best-absorbed forms.
Food sources of magnesium: pumpkin seeds, almonds, dark chocolate, spinach, bananas, black beans, and whole grains.
Can You Take a Single Prenatal Multivitamin Instead?
Many prenatal multivitamins combine several of these nutrients in one tablet — convenient, but check the label carefully. Most multivitamins don't contain enough iron or omega-3 DHA to meet pregnancy needs and may need to be supplemented individually.
In Baby Novum, you can track each supplement, set daily reminders, and log whether you've taken them — so you never miss a dose.
Supplements work alongside diet rather than replacing it, so it is worth reading this next to the safe foods guide — particularly the vitamin A caution, which applies to both liver and retinol-form supplements. Your care provider will also check iron levels at routine appointments through the second trimester, which is the point at which a deficiency usually shows up.
FAQ — Prenatal Supplements
Do I need to take a prenatal vitamin if I already eat well?
Almost certainly yes. Folic acid and iodine needs in particular rise sharply in pregnancy to levels that are genuinely difficult to reach through diet alone, and the neural tube — where folic acid matters most — closes by around week 6, often before many people know they are pregnant. A good diet is not a substitute for supplementation in the first trimester specifically.
Can I take too much of a prenatal vitamin?
Yes — more is not automatically better, and some vitamins are genuinely risky in excess. Vitamin A in particular should come from beta-carotene rather than retinol in supplement form during pregnancy, since high-dose retinol has been linked to birth defects. Stick to the dosage on a prenatal-specific product rather than combining multiple general multivitamins.
When should I start taking folic acid?
Ideally before conception, or as soon as you start trying — the neural tube forms and closes in the first few weeks, often before a positive pregnancy test. If you are already pregnant and have not started yet, begin immediately rather than waiting for a first appointment; every day from here still matters.
Is a single prenatal multivitamin enough, or do I need separate supplements?
Often not quite. Most prenatal multivitamins fall short on iron and omega-3 DHA specifically, since fitting the full pregnancy dose of either into one tablet alongside everything else is difficult — check the label against the target amounts and expect to supplement those two separately in many cases.